Hydrocrackers have always produced environmentally friendly products, even before environmental regulations on products increased. No other process can take low value, highly aromatic, high sulfur, and high nitrogen feedstocks and produce a full slate of desirable sweet products: LPG, high quality diesel fuel, hydrogen-rich FCC feed, ethylene cracker feed, and/or premium lube unit feedstocks.
Modern hydrocracking was commercialized in the early 1960's. These early units converted light feedstocks (from atmospheric crude towers) into high-value, high-demand gasoline products. In addition, high hydrocracker volume gain (exceeding 20%) added significantly to the refinery bottom line. Because of these strong attributes, hydrocracker capacity has increased steadily over the years.
Increased environmental regulations on gasoline and diesel have made hydrocracking the most essential process resulting in ever greater increases in worldwide capacity. The most recent grassroots hydrocrackers were designed to maximize the production of middle distillates from increasingly difficult feedstocks such as FCC LCO, Heavy Vacuum Gasoils, and Heavy Coker Gas Oils. Like their predecessors, most modem hydrocrackers produce high-value, environmentally friendly distillate products including massive volumes of ultra-low sulfur diesel (ULSD), even with progressively more demanding feedstocks Early generation hydro crackers were in the 10,000 barrel-per-day range while many new units today exceed 100,000 barrels per day.
Growing demand for middle distillates, declining market for high sulfur fuel oil, and increasingly stringent environmental regulations are putting refineries, especially those with lower Nelson Complexity Index, under immense margin pressures and even forcing many to shut down. This recent trend has led to grassroots projects for distillate-oriented conversion technologies. Very few, if any, refineries have their conversion strategy focused on FCC technology, and many FCC units are operating in low severity distillate mode or are occasionally being converted to a propylene producer. Hydrocracking offers greater flexibility to process opportunity crudes while producing premium grade clean fuels which improves refinery margins.
Some refineries have tried to solve the difficulties in dealing with heavy feedstocks by building two separate hydrocracker, one for lube and one for fuels. Another solution investigated was to just hydrotreat the thermally cracked gas oil and then feed the hydrotreated gas oil to FCC and install a high conversion hydrocracker and take a large bleed of UCO to lube base oil production. Others have proposed to solvent deasphalt the residuum feed and process only the deasphalted oil in a Resid Hydrocracking Unit (RHU), e.g., ebullated-bed hydrocracking. Also, others have processed the unconverted vacuum resid from a Resid Hydrocracking Unit in an SDA Unit and recycled the DAO back to the front end of the RHU or further treating the DAO in a residue fixed-bed hydrotreatment unit to produce low sulfur fuel oil or feed to a FCC unit.